Fabio Nussberger, MD, and colleagues at the University of Bern in Switzerland studied 418 patients who underwent ESWL. Ultrasound scans at post-treatment day 1 revealed renal hematomas in 39 (9%) patients. For 37 of them, the researchers selected a control group of patients without hematoma who were matched by age, gender, and number and energy of shock waves, stone burden, and localization. In the hematoma group, significantly more patients had a high BMI (greater than 30 kg/m2) and a low BMI (less than 21.5 kg/m2) compared with the control group. Renal hematomas developed in all patients with a BMI less than 21. 5 kg/m2.

The cases and controls did not differ significantly with respect to skin-kidney distance and rates of diabetes, discontinued anticoagulant/antiplatement medications, and arterial hypertension, according to the investigators.